Microphone



- April 1957 Y D. D. MESHIRER ETAL 2,787,675

I MICROPHONE Filed April 2, 1954 4 Sheets-Sheet 1 FIGS.

Zj mv/o o. Mes/41252 041.5 QUL/CK BY 21 INVENTORS.

April 2, 1957 D. D. MESHIRER ET AL MICROPHONE I 4 Sheets-Sheet 2 FiledApril 2, 1954 FIG.5.

FIGA.

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37' no. IO.

INVENTORS. DAV/D D. MESH/QEQ" DALE quL/cK BY 3 w ATTIOEMFX April 2, 1957D, D, s m ET AL 2,787,675

' MICROPHONE Filed April 2, 1954 4 sheets-sheet 5 54 INVENTORS 7 Y"DAVID oar 55am DALE 11s BY 6 JTTQQNEX April 2, 1957 I D. D. MESHIIARERETAL 2,787,675

MICROPHONE Filed April 2 1954 I 4 Sheets-Sheet 4 INVENTORJ'. DAV/D 0.MESH/25.2

0A4: quuc/r' ATTOQME'X United States Patent MICROPHONE David D.Meshirer, Jackson Heights, and Dale Gulick, Farmingdale, N. Y.

Application April 2, 1954, Serial No. 420,698

18 Claims. (Cl. 179-179) This invention relates to microphones, and moreparticularly, to a microphone for use in aircraft and for similarpurposes.

An object of the invention is to provide a microphone of the characterdescribed having a novel construction whereby the cover may be taken offand the switch unit or transmitter unit removed for replacement orrepair by quickly and easily sliding said cover and units out of thecasing and without requiring any time-consuming unscrewing or otherdisassembly operations.

Another object is to provide a microphone construction wherein all theparts, except the switch and transmitter units may be made ofnon-metallic material, preferably plastic, and completely eliminatingscrews or other metallic fastening elements.

A further object is to provide a microphone comprising a casing forhousing the operating components, said casing being completely closedand sealed off from the atmosphere so as to protect said components frommoisture, dust, and the like.

Still another object is to provide the casing with a wall portion havingan opening therethrough, switchactuating means extending through saidopening, and means sealing said opening for preventing dust and moisturefrom entering the interior of the casing therethrough.

A further object is to provide in a microphone of the characterdescribed, a non-metallic bushing secured in said opening, saidswitch-actuating means comprising a push button member reciprocallyslidable within said bushing and having an inner end engaging the switchand an outer end outwardly of the casing, said sealing means comprisinga flexible non-metallic sealing element surrounding said button memberand having one end in sealed relation to said bushing and the oppositeend in sealed relation to said button member.

Another object is to provide a' novel means for retaining thetransmitter unit in fixed position within the casing but permitting saidunit to be easily removed there from for replacement or repair.

Still another object is to provide a novel electrical cord constructionand mounting means in the casing therefor to permit rapid and easyinsertion or removal of the electrical cord with respect to the casing.

A further object is to provide a novel arrangement for mounting thecover member in sealed engagement with the open end of the casing andpermitting the cover to be quickly and easily removed or reassembled.

Another object is to provide a microphone of the character described,said open end of the casing being of cylindrical configuration, saidcover member having a cylindrical portion'extending Within saidcylindrical casing end and removable therefrom, and resilient annularsealing means engaging said cylindrical casing end and said covercylindrical portion.

Still another object is to provide a microphone of thecharacterdescribed, wherein the casing has a wall portion with an openingtherethrough, a resilient nonice metallic sleeve extending through saidopening and in sealing engagement therewith, and an electric cordextending through said sleeve and comprising a plurality of electricalwires connected to the transmitter unit and the switch, whereby theopening will be sealed so as to prevent dust, moisture and otherdeleterious substances of the atmosphere from entering the interior ofthe casing.

A furtherobject is to provide the sleeve with an enlarged non-circularhead, thecasing having a non-circular recess receiving said head toprevent rotation or twisting of the sleeve and the electrical cordrelative to the casing.

Other objects and advantages will be apparent as the descriptionproceeds in connection with the accompanying drawings wherein:

Fig. 1 is a front elevational view of an embodiment of the invention;

Fig. 2 is a sectional view on line 22 of Fig. 3;

Fig. 3 is a rear elevational view with the cover member removed forclarity in illustration;

Fig. 4 is a detail view of the cover member;

Fig. 5 is a detail view of the switch-actuating push button member;

Fig. 6 is a detail sectional view of an O-ring;

Fig. 7 is a partially sectioned view of a guide bushing for the pushbutton member;

Fig. 8 is a partially sectioned view of a tubular sealing element forthe push button member;

Fig. 9 is a detail sectional view of another O-ring;

Fig. 10 is a detail sectional view of a spacer element;

Fig. 11 is a perspective view of another embodiment of the invention andshows the several components in disassembled relation;

Fig. 12 is a front elevational view of the device of Fig. 11;

Fig. 13 is a vertical sectional view on line 1313 of Fig. 12;

Fig. 14 is a rear elevational view of the second embodirnent with thecover member removed;

Fig. 15 is a detail view of the push button member; and

Fig. 16 is a detail perspective View of a cylindrical support member formounting several of the components of the second embodiment.

Referring to the drawing in more detail, reference numeral 11 indicatesgenerally a first form of a microphone embodying the present inventionand comprising a casing 12. The latter is preferably formed of plasticor similar non-metallic material and comprises an outer cylindrical wall13. At one end of casing 12 is a mouthpiece portion 14 comprising arelatively thin wall 15 extending transverse to the axis of casing 12and surrounded by a peripheral annular ridge 16.

A conical wall 17 connects wall 15 to cylindrical wall 13. A pluralityof projections 18 to 24 extend from wall 17 parallel to the axis ofcasing 12 to the opposite open end thereof and have end faces lyingapproximately in a transverse common plane with the end face 25 ofcylindrical Wall 13. It will be seen that projections 18-24 are arcuatein transverse section and extend in annular form parallel to wall 13 butspaced inwardly therefrom to provide an annular space 26 between wall 13and projections 18-24. The latter are also spaced from each other toprovide radially extending slots therebetween.

The inner arcuate surfaces 18'-24' of projections 18-24 cooperate toform a substantially cylindrical but discontinuous interior wall surface33 enclosing a cylindrical interior space within casing 12. Mountedwithin this space is a carbon button diaphragm unit or transmitter unit27 of well-known construction, such as the 'Western Electric Co.transmitter unit. This unit 27' serves the function of converting soundwaves into electrical impulses.

Mouthpiece wall is provided with a plurality of apertures 28therethrough. A diaphragm 29 of thin plastic sheet material is mountedagainst the rear or inner surface 36 of wall 15 to seal apertures 23 andthereby prevent dust or moisture from entering the interior of casing12. The front face 31 of transmitter unit 27 abuts against diaphragm 29.

Transmitter unit 27 comprises a first cylindrical portion 32 slidablyengaging the cylindrical interior wall surface 33. Extending rearwardlyfrom portion 32 is a reduced second cylindrical portion 34 forming ashoulder 35. An annular O-ring 36 of resilient material such as rubbersurrounds portion 34 and abuts against shoulder 35. Au annular spacerelement 37 of similar material abuts against O-ring 36 to retaintransmitter unit 27 securely in its assembled position as will beexplained in more detail below.

As seen in Fig. 3, the arcuate inner surfaces 18', 19', and 23 ofprojections 18, 19, 20, 23 are each provided with an axially extendingnotch at 38, 39, 40, 41, respectively, for slidably receiving the fourcorners of an enclosed switch unit 42 such as the standard No. 1 GeneralElectric Co. Switchette. The front surface 43 of switch unit 42 abutsagainst the rear edge 37 of spacer element 37 to retain the latteragainst outward movement relative to casing 12. The rear surface 44 ofswitch unit 42 is substantially co-planar with end face of outercylindrical wall 13.

Referring to Fig. 4, a circular cover member 45 of plastic or othernon-metallic material is provided with a planar surface 46 from whichextends a hollow cylindrical portion 47. The latter is provided on itsexterior surface with a first peripheral groove 48 adjacent planarsurface 46 and a second peripheral groove 49 adjacent the forward end 50of cylindrical portion 47. 1

As shown in Fig. 2, the interior wall surface 51 of outer cylindricalwall 13 is enlarged or counterbored at 52 adjacent the rear end ofcasing 12 to provide an annular shoulder 53. When cover member 45 is tobe assembled to casing 12, a second resilient O-ring 54, preferably ofrubber, is first placed in groove 49 and cylindrical cover portion 47 isinserted into the annular space 26 until shoulder 53 abuts O-ring 54 tosnap the latter rearwardly from groove 49 into its final position withinthe rear groove 48 in which position O-ring 54 will tightly engage thecounterbored surface 52 to seal the rear end of casing 12 from theatmosphere and to retain cover member 45 securely in place.

In this final assembled position planar surface 46 of cover member 45abuts against end face 25 of casing wall 13 and also against rearsurface 44 of switch unit 42 to retain the latter against outwardmovement with respect to casing 12 and thereby also retaining spacerelement 37. O-ring 36, and transmitter unit 27 in proper assembledposition. It will thus be seen that cover member 45 may be quickly andeasily removed, preferably by prying it with a screw driver, and switchunit 42 and transmitter unit 27 may be slidably removed and replaced byother units. Thus the operative electrical components may be easilyreplaced without time-consuming unscrewing or other disassemblyoperations.

Cylindrical wall 13 is provided with an opening 56 extending radiallytherethrough. A cylindrical guide bushing 57 of plastic or similarnon-metallic material is press-fitted within opening 56. The outersurface 58 of wall 13 is counterbored at 59 around opening 56. The loweror inner end of guide bushing 57 is provided with a peripheral groove60.

A plastic push button 61 is provided with an enlarged head portion 62integral with a cylindrical shaft portion 63 reciprocally slidable inguide bushing 57. Shaft portion 63 is provided with a peripheral groove64 receiving 4 an annular clip 65 adapted to abut the lower end face 66of bushing 57 to limit upward movement of push button 61.

A tubular sealing element 67 of flexible non-metallic material isprovided with an upper lip 68 bent inwardly to engage within groove 60of bushing 57. The lower end of element 67 is bent inwardly at 69 andthen upwardly at 70 in direction parallel to but spaced inwardly fromthe cylindrical wall 71 of element 67. The inner cylindrical portion 70of sealing element. 67 is in sealed gripping engagement with the lowerend of push button shaft portion 63. It will thus be seen that air, dustand moisture which may pass through the inevitable clearance spacebetween button shaft portion 63 and bushing 57 will be prevented fromentering the interior of casing 12, thereby protecting the severaloperative components therein.

Push button head portion 62 is provided with an integral peripheralflange 72 received by counter-bore 59 when the button 61 is depressed.The lower end face 73 of shaft portion 63 engages a button 74 of switchunit 42 to actuate the latter in a conventional manner well-known in theart.

Wall 13 is further provided with a cylindrical radial opening 75diametrically opposite to opening 56. A flexible plastic or rubberstrain relief sleeve 76 is provided with a. cylindrical portion 77extending through opening 75 and having an enlarged square head 78 onthe inner end thereof to retain sleeve 76 against outward movementrelative to casing 12. Sleeve 76 is fixedly secured to an insulatedelectrical cord 79 having a plurality of electrical wires which areconnected to the terminals of units 27 and 42 in the usual manner toform the desired electrical circuit.

The inner surface of casing outer wall 13 is provided with a rectangularrecess receiving head 78 so as to prevent sleeve 76 and cord 79 fromrotating and twisting relative to casing 12. Sleeve 76 is preferablymade of rubber and is molded around cord 79 to provide a durableassembly therewith. Sleeve 76 also sen/es to seal opening 75 so as toprevent dust, moisture and other deleterious substances of theatmosphere from entering the interior of casing 12.

Referring now to Figs. 11 to 16 inclusive, the reference numeral 111indicates generally a second form of microphone embodying the presentinvention.

It will be noted that those parts of microphone 111 which are similar tothe parts of microphone 11 described above, will be given correspondingreference numerals raised by units over the reference numerals of thefirst form of the invention.

Microphone 111 comprises a casing 112 preferably formed of plastic orsimilar non-metallic material, and having an outer cylindrical wall 113.At one end of casing 112 is a mouthpiece portion 114 comprising arelatively thin wall 115 extending transversely to the axis of casing112, and surrounded by a peripheral annular ridge 116. An approximatelyconical wall 117 joins transverse wall 115 to cylindrical wall 113.

The interior of casing 112 is hollow and is formed with a cylindricalinterior wall surface 133 adjacent mouthpiece portion 114. A transmitterunit 127 similar to unit 27 described above, is mounted within the spaceenclosed by wall surface 133, and comprises an enlarged cylindricalportion 132 slidably engaging the cylindrical interior wall surface 133.Extending rearwardly from portion 132 is a reduced second cylindricalportion 134 forming a shoulder 135 at its junction with portion 132.

Mouthpiece wall 115 is provided with a plurality of apertures 128extending therethrough. The transmitter unit 127 comprises a diaphragm129 of thin plastic sheet material adapted either to abut or to lieadjacent the rear inner surface 130 of mouthpiece wall 115. Diaphragm129 serves to seal off apertures 128 and thus prevent dust or moisturefrom entering the interior of casing 112. However, diaphragm 129 issuificiently flexible so as to permit sound waves to'pass therethrough.

As best seen in Fig. 16, a cylindrical support member, indicatedgenerally at 201, is formed of non-metallic material, preferablyplastic, and serves in microphone 111 substantially the same function asthe annular means comprising O-ring 36 and annular spacer element 37 ofmicrophone 11. The internal diameter of support member 201 is slightlylarger than the external diameter of reduced cylindrical portion 134 oftransmitter unit 127 whereby the front end 202 of support member 201extends around the transmitter portion 134 and slidably receives thelatter so as to abut against the shoulder 135.

A pair of rectangular slots 203, 204 extend longitudinally of supportmember 201 from the opposite end 205 thereof. Slots 203, 204 aredisposed diametrically opposite each other and are adapted to receive aswitch unit 142 which is substantially similar to switch unit 42described above with respect to microphone 11. It will be seen thatswitch unit 142 is of rectangular shape in cross-section and snugly fitswithin slots 203, 204 so as to abut against the inner surfaces 203', 204of the latter.

As best seen in Fig. 14, switch unit 142 is of a length greater than theexternal diameter of cylindrical support member 201 whereby the oppositeends of switch unit 142 project radially outwardly from the latter. Apair of contacts 207, 208 project upwardly from one of the outer ends209 of switch unit 142 and the opposite end 210 thereof is provided witha projecting contact 211. Soldered to contacts 208, 211 are a pair ofelectrical wires 213, 214, respectively. A third wire 212 is soldered atone end to contact 207 and at its opposite end to one of the contactterminals (not shown) of transmitter unit 127. A fourth wire 215 issoldered at its inner end to the other contact terminal of transmitterunit 127. As best seen in Fig. 11, wires 212, 214 and 215 are enclosedby a sheath of insulation 216 so as to comprise therewith an electricalcord indicated generally by the reference numeral 179.

The electrical cord 179 extends through a hollow rubber sleeve 176similar to sleeve 76 described above, and preferably molded of rubberand fixedly secured around cord 179. The sleeve 176 is slightly conicalin shape and projects through a circular opening 217 extending radiallythrough the cylindrical wall 113 of casing 112. The inner end of opening217 communicates with a square recess 218 formed in the interior surface113 of wall 113.

. The inner end of sleeve 176 is formed integral with an enlarged squarehead 178 which fits within recess 218 so as to prevent rotation ortwisting of sleeve 176 and cord 179 relative to casing 112. Theengagement of head 178 with the bottom of recess 218, and also theengagement of sleeve 176 with the interior surface of opening 217 sealsoff the latter so as to prevent moisture, dust and other atmosphericingredients from entering into the interior of casing 112.

Referring again to Fig. 16, support. member 201 is further provided witha slot 220 extending from its end 202 for receiving the button shank 234to be described below. A series .of smaller slots 221, 222 and 223 alsoextend from the end 202. The intermediate slot 222 receives the innercylindrical portion 224 projecting from head 178 of sleeve 176 when thevarious components are in the assembled relation shown in Figs. 13 and14. Slot 223 receives wires 212, 213 extending therethrough and slot 221similarly receives wire 214, thereby maintaining wires 212, 213, 214 inproperly assembled relation within casing 112.

Microphone 111 is further provided with a circular cover member 145which is of similar construction to cover member 45 described above andhence the various constructional details of cover member 145 and themeans for securing it to the open end of casing 112 will not bedescribed, reference being made to the description of Figs. 1 toinclusive for this aspect of the device so as '6 to avoid repetition.member 145 engages switch unit 142 so as to urge the latter inwardly.Switch 142 in'turn abuts against surfaces 203', 204' of slots 203, 204so as to urge the opposite end of support member 201 against shoulder oftransmitter unit 127 and thereby maintain the latter and diaphragm 129in assembled relation against mouthpiece wall 115.

It will be seen in Fig. 11 that after removal of cover member 145,switch unit 142 may be removed from slots 203, 204 of support member201. The latter may then be removed so as to permit the withdrawal oftransmitter unit 127 and all of the operative components will then be inthe disassembled relation shown in Fig. 11, thereby permitting easyremoval and access to the various components for repair or replacementthereof. It will also be seen that sleeve 176 together with cord 216 maybe pulled inwardly through opening 217 towards the interior of casing112 and may then be removed outwardly through the open end of the latterfor replacement or repair of cord 216.

As shown in Fig. 13, another cylindrical opening 230 extends throughcasing wall 113 in a radial direction and is located diametricallyopposite opening 217. The interior surface of wall 113 is provided witha radially inwardly projecting boss 231 so as to increase the bearinglength of opening 230. The upper end of the latter communicates with anenlarged counterbore 231a extending radially inwardly from the exteriorsurface of easing wall 113. A cylindrical non-metallic bushing 232 ispress-fitted within counterbore 231 and is provided with an outer endprojecting outwardly from the exterior surface 113 of wall 113.

A push button indicated generally at 233 comprises a cylindrical shank234 extending through bushing 232 and also through opening 230 and isreciprocally slidable therein. The lower end of shank 234 engages button174 of switch unit 142. A circular groove 235 is formed on anintermediate portion of shank 234 and engageably receives an 0-ring 236which abuts boss 231 so as to' limit the outward movement of push button233.

Integral with the outer end of shank 234 is an enlarged head portion 237adapted to be engaged by the finger of the operator in order to depresspush button 233 so as to actuate button 174 of switch unit 142. Theperiphery of head portion 237 is integrally formed with a cylindricalflange 238 extending radially inwardly and adapted to slide over theoutwardlyprojecting portion of bushing 232 so as to aid in guiding pushbutton 233 in its reciprocal sliding movement.

An annular sealing element 240 of flexible non-metallic materialpreferably rubber, surrounds the upper end of a shank 234 and isprovided wtih a suitable central aperture receiving the latter. Theouter peripheral edge of sealing element 240 is clampingly engagedbetween the inner end of bushing 232 and the inner surface 231' ofcounterbore 231, whereas the edge of the central opening of sealingelement 240 is fixedly sealed to an upper portion of shank 234. It willthus be seen that sealing element 240 seals off opening 230 so as toprevent dust, moisture and other deleterious atmospheric substances fromentering the interior of casing 112.

It is to be understood that the specific embodiment through, a thinflexible non-metallic diaphragm within It will be understood that cover,

answers said casing and lying adjacent the interior surface of said walland sealing off said apertures but permitting sound waves to passtherethrough, a transmitter unit within said casing and adjacent saiddiaphragm, a switch within said casing and operatively connected to saidtransmitter unit, said casing having a wall portion with an openingtherethroug'h, switch-actuating means :extending through said openingand movable therein for controlling said switch, means sealing saidopening for preventing dust and moisture from entering the interior ofthe .casing therethrough, an end of said casing being open, anon-metallic cover member secured to the casing and sealing off saidopen end thereof from the atmosphere, comprising a nonmetallic bushingsecured in said opening, said switch-actuating means comprising a pushbutton member reciprocally slidable within said bushing and having aninner end engaging the switch and an outer end projecting outwardly ofthe casing, said -seal ing means comprising a flexible non-metallicsealing element surrounding said button member and having one end insealed relation to said bushing and the opposite end in sealed relationto said button member, said bushing being provided with an annulargroove, the inner end of said button member having a cylindrical shank,said one end of the sealing element being secured within said groove,said opposite end of the sealing element comprising an approximatelycylindrical wall and being provided with an annular flange portionspaced radially inwardly from and extending parallel to said cylindricalwall, said flange portion being in sealed engagement with saidcylindrical shank of the button memher.

2. A microphone comprising a hollow casing formed of non-metallicmaterial, and one end of said casing having a mouth-piece portionincluding a wall of said casing, said wall having a plurality ofapertures therethrough, a thin flexible non-metallic diaphragm withinsaid casing and lying adjacent the interior surface of said wall andsealing of]? said apertures but permitting sound waves to passtherethrough, a transmitter unit within said casing and adjacent saiddiaphragm, a switch within said casing and operatively connected to saidtransmitter unit, said casing having a wall portion with an openingtherethrough, switch-actuating means extending through said opening andmovable therein for controlling said switch, means sealing said openingfor preventing dust and moisture from entering the interior of thecasing therethrough, an end of said casing being open, and a nonmetalliccover member secured to the casing and sealing off said open ,endthereof from the atmosphere, said casing being provided with acylindrical hollow interior adjacent said diaphragm, said transmitterunit being located within said cylindrical casing interior coaxialtherewith and having a first cylindrical portion adjacent said diaphragmand of a diameter approximately equal to the diameter of saidcylindrical interior, said transmitter unit having a second cylindricalportion with a diameter less than said diameter of the cylindricalcasing interior, the junction of said cylindrical portions forming ashoulder, annular non-metalic means extending around said secondcylindrical portion and having a surface engaging said shoulder andanother surface engaging an inner end of said switch, said cover memberengaging the outer end of said switch.

3. A microphone comprising a hollow casing formed of non-metallicmaterial, and one end of said casing having a mouthpiece portionincluding a wall of said casing, said wall having a plurality ofapertures therethrough, a thin flexible non-metallic diaphragm withinsaid casing and lying adjacent the interior surface of said wall andsealing off said apertures but permitting sound waves to passtherethrough, a transmitter unit within said casing and adjacent saiddiaphragm, a switch within said casing and operatively connected to saidtransmitter unit, said casinghaving a wall portion with an openingtherethrough,

switch-actuating means extending through said opening and movabletherein for controlling said switch, means sealing'said opening forpreventing dust and moisture from entering the interior of the casingtherethrough, an end of said casingbeing open, a non-metallic covermember secured to the casing and sealing off said open end thereof fromthe atmosphere, said open end of the casing being of cylindricalconfiguration, said cover member having a cylindrical portion extendingwithin said cylindrical casing and removable therefrom, and resilientannular sealing means engaging said cylindrical casing end and saidcover cylindricalportion, said cover cylindrical por tion being providedon the exterior surface thereof with an annular groove, said annularsealing means lying within said groove and engaging the interior surfaceof said cylindrical casing open end, said cover cylindrical portionbeing provided with a second annular groove spaced axially inwardly ofthe first-recited groove, said annular sealing means comprising a-ringand adapted to be placed in said second annular groove when the covermember is disassembled from the casing and movable into saidfirst-recited groove as said cover cylindrical portion is inserted intosaid cylindrical casingopen end.

4. The combination of claim 3, the interior surface of said cylindricaleasing open end being provided with a radially inwardly projectingabutment means engageable with said ring for moving the latter from saidsecond groove to said firstq-ecited groove as said covercylindricalportion is inserted into said cylindrical casing open end.

5. A microphone comprising a hollow casing formed of plastic material,one end of said casing having a mouthpiece portion including a wall ofsaid casing, said wall having a plurality of apertures therethrough, athin flexible non-metallic diaphragm 'within said casing and lyingadjacent the interior surface of said wall and sealing off saidapertures but permitting sound waves to pass therethrough, a transmitterunit within said casing and adjacent said diaphragm, a switch withinsaid casing and operatively connected to said transmitter unit, saidcasing being provided with a cylindrical hollow interior adjacent saiddiaphragm, said transmitter unit being located within said cylindricalcasing interior and coaxial therewith and having a first cylindricalportion adjacent said diaphragm and of a diameter. approximately equalto the diameter of said cylindrical interior,.said transmitter unithaving a second cylindrical portion with a diameter less than saiddiameter of the cylindrical casing interior, the junction of saidcy1indrical portions forming a shoulder, annular non-metallic resilientmeans extending around said second cylindrical portion and having asurface engaging said shoulder and another surface engaging an inner endof said switch, said cover member engaging the outer end of said switch,said annular means comprising a resilient ring engaging said secondcylindrical portion and said shoulder and a resilient annular spacerring located between and contacting said ring and said inner end of theswitch.

6. Amicrophone comprising a hollow casing formed of plastic material andhavingan open end, a transmitter unit within said casing, a switch.within said casing and operatively connected to said transmitter unit,a plastic cover member secured to the casing and sealing off said openend thereof from the atmosphere, said casing being providcd with acylindrical hollow interior adjacent said diaphragm, said transmitterunit being located within said cylindrical casing interior coaxialtherewith and having a first cylindrical portion adjacent said diaphragmand of a diameter approximately equal to the diameter of saidcylindrical interior, said transmitter unithaving a second cylindricalportion with a diameter. less than said diameter of the cylindricalcasing interior, the junction of Said cylindrical portion forming ashoulder, annular nonmetallic resilient means extending aroundsaidsecond cylindrical portion and having a surface engaging said shoulderand an opposite surface engaging an inner end of said switch, said covermember engagingthe outer end of said switch, said annular meanscomprising a resilient ring engaging said second cylindrical portion andsaid shoulder and a resilient annular spacer ring located between andcontacting said ring and said inner end of the switch, said switch andsaid transmitter unit being slidably mounted within the casing foroutward movement through the open outer end thereof when the covermember is removed.

7. A microphone comprising a hollow casing formed of plastic material, atransmitter unit within said casing, a switch within said casing andoperatively connected to said transmitter unit, an end of said casingbeing open, and a plastic cover member secured to the casing and sealingofi said open end thereof from the atmosphere, said open end of thecasing being of cylindrical configuration, said cover member having acylindrical portion extending within said cylindrical casing open endand removable therefrom, and resilient annular sealing means engagingsaid cylindrical casing open end and said cover cylindrical portion,said cover cylindrical portion being provided on the exterior surfacethereof with an annular groove, said annular sealing means lying withinsaid groove and engaging the interior surface of said cylindrical casingopen end, said cover cylindrical portion being provided with a secondannular groove spaced axially inwardly of the first-recited groove, saidannular sealing means comprising a ring and adapted to be placed in saidsecond annular groove when the cover member is disassembled from thecasing and movable into said first-recited groove as said covercylindrical portion is inserted into said cylindrical casing open end.

8. A microphone comprising a hollow casing formed of plastic material, atransmitter unit within said casing, a switch within said casing andoperatively connected to said transmitter unit, an end of said casingbeing open, and a plastic cover member secured to the casing and sealingoff said open end thereof from the atmosphere, said open end of thecasing being of cylindrical configuration, said cover member having acylindrical portion extending within said cylindrical casing open endand removable therefrom, and resilient annular sealing means engagingsaid cylindrical casing open end and said cover cylindrical portion,said cover cylindrical portion being provided on the exterior surfacethereof with an annular groove, said annular sealing means lying withinsaid groove and engaging the interior surface of said cylindrical casingopen end, said cover cylindrical portion being provided with a secondannular groove spaced axially inwardly of the first-recited groove, saidannular sealing means comprising a ring and adapted to be placed in saidsecond annular groove when the cover member is disassembled from thecasing and movable into said first-recited groove as said covercylindrical portion is inserted into said cylindrical casing open end,the interior surface of said cylindrical casing open end being providedwith a radially inwardly projecting abutment means engageable with saidring for moving the latter from said second groove to said first-recitedgroove as said cover cylindrical portion is inserted into saidcylindrical casing open end.

9. A microphone comprising a hollow casing formed of non-metallicmaterial, and one end of said casing having a mouthpiece portionincluding a wall of said casing, said wall having a plurality ofapertures therethrough, a thin flexible non-metallic diaphragm withinsaid casing and lying adjacent the interior surface of said wall andsealing off said apertures but permitting sound waves to passtherethrough, a transmitter unit within said casing and adjacent saiddiaphragm, a switch within said casing and operatively connected to saidtransmitter unit, said casing having a wall portion with an openingtherethrough, switch-actuating means extending through said opening andmovable therein for controlling said switch, means sealing said openingfor preventing dust and moisture from entering the interior of thecasing therethrough,

an end of said casing being open, and a non-metallic cover membersecured to the casing and sealing ofl? said open end thereof from theatmosphere, said housing being provided with a cylindrical hollowinterior adjacent said diaphragm, said transmitter unit being locatedwithin said cylindrical casing interior coaxial therewith and having afirst cylindrical portion adjacent said diaphragm and of a diameterapproximately equal to the diameter of said cylindrical interior, saidtransmitter unit having a second cylindrical portion with a diameterless than said diameter of the cylindrical casing interior, the junctionof said cylindrical portions forming a shoulder, annular non-metallicmeans extending around said second cylindrical portion and having asurface engaging said shoulder and another surface engaging an inner endof said switch, said cover member engaging the outer end of said switch,said annular means comprising a cylindrical support member having thefirst-recited surface at one end thereof and slots extending from theopposite end thereof for receiving said switch and supportably mountingthe latter, said switch projecting outwardly beyond said opposite end ofthe support member so as to be engaged by said cover member.

10. A microphone comprising a hollow casing formed of non-metallicmaterial, and one end of said casing having a mouthpiece portionincluding a Wall of said casing, said wall having a plurality ofapertures therethrough, a thin flexible non-metallic diaphragm withinsaid casing and lying adjacent the interior surface of said wall andsealing ofi said apertures but permitting sound waves to passtherethrough, a transmitter unit within said casing and adjacent saiddiaphragm, a switch within said casing and operatively connected to saidtransmitter unit, said casing having a Wall portion with an openingtherethrough, switch-actuating means extending through said opening andmovable therein for controlling said switch, means sealing said openingfor preventing dust and moisture from entering the interior of thecasing therethrough, an end of said casing being open, and anon-metallic cover member secured to the casing and sealing off saidopen end thereof from the atmosphere, said casing having a wall portionwith a second opening therethrough, a resilient non-metallic sleeveextending through said second opening and in sealing engagementtherewith, and an electrical cord extending through said sleeve andcomprising a plurality of electrical wires connected to said transmitterunit and said switch.

11. A microphone as recited in claim 10 wherein said sleeve is providedwith an enlarged non-circular head, said casing having a non-circularrecess receiving said head to prevent rotation of the sleeve and cordrelative to the casing.

12. A microphone as recited in claim 11 wherein said sleeve and head areintegrally formed of rubber and said sleeve is fixedly secured to saidelectrical cord extending therethrough.

13. In a microphone as recited in claim 9, said casing having a wallportion with a second opening therethrough, a resilient non-metallicsleeve extending through said second opening and in sealing engagementtherewith, and an electrical cord extending through said sleeve andcomprising a plurality of electrical wires connected to said transmitterunit and said switch, said support member having means engaging theportions of said wires within the casing for maintaining said wireportions in assembled position within the casing.

14. A microphone comprising a hollow casing formed of non-metalicmaterial, said casing having a front apertured wall, and an annular wallextending rearwardly from the periphery of said front wall, andintegrally formed therewith, said casing being open at its rear end,said casing being formed with an internal cylindrical recess, atransmitter unit fitted in said recess and adjacent said front wall,means Within said casing formed with a pair of horizontally aligned,rearwardly opening notches, a switch unit in the casing having its endsslidably received in-said notches, a non-metallicback cover removablymounted on the rear open end of the casing and serving to retain theswitch unit within said notches, and whereby removal of the back coverwill permit sliding of said switch unit as a whole, rearwardly, out ofsaid notches and through said rear open end of the casing, and whereby,Withdrawal of the switch unit will permit, pulling out the transmitter,said annular wall having an opening, a switch actuating button memberslidably mounted in said opening and depressable to actuate said switchunit, said casing having a second opening, a sleeve slidably passingthrough said second opening, a cord attached to said sleeve andcomprising wiring operatively connected to said switch unit andtransmitter.

15. The combination of claim 14, the means formed with the switchcomprising a cylindrical member of unmetallic material having one endslidably received in said cylindrical recess and contacting the back ofsaid transmitter, and said cylindrical member extending to said backcover and being formed with an opening through which the "switchactuating button member passes, and an opening through which said sleevepasses.

'16. The combination of claim 14, said sleeve having a non-circulardeadnon-rotatably engaged within a noncireular recess in said annular wallof said casing at said bottom opening.

17. The combination of claim 16, means to seal said back cover to saidcasing, means to seal the opening through which said switch actuatingbutton member passes into said casing, and said sleeve and head, andsaid sleeve having a forward portion adjacent said head to seal theopening in the casing through which said sleeve passes.

18. The combination of claim 14, in combination with a non-metallicdiaphragm fitted in said cylindrical recess and interposed between saidtransmitter and front wall and covering'the operations in said frontwall.

References Cited in the file of this patent UNITED STATES PATENTS BlountMay 5, 1936 2,267,364 Blount Dec. 23, 1941

